Screan And Effect Analysis Of Immunostimulants For Large Yellow Croaker, Pseudosciaena Crocea

Large yellow croaker(Pseudosciaena crocea) is one of the most economically important marine fish in China. With the rapid development of intensive farming of large yellow croaker, disease, germplasm and environment are becoming the most significant problems. Diseases had led to mass mortality of culture large yellow croaker and considerable economic losses. Immunostimulant, which has been demonstrated to be non-polluting, non-specific and easy use, becomes an important measure for disease control in aquaculture. This article aims to screen the immunostimulants which can improve immunity and disease resisttance of large yellow croaker. The results are summarized as follows:The yeast cell wall polysaccharide and compound immunostimulants(including chitin, yeast, selenium, and alginic acid), respectively, according to a certain mixing ratio were added to the basic diet of large yellow croaker. Feeding experiments were carried out in seawater floating cages for a period of 49 days to investigate the effects of the yeast cell wall polysaccharide and compound immunostimulants on immunity and disease resistance of large yellow croaker. The results show that when compared with the control group, serum bactericidal activity of large yellow croaker, lysozyme, acid phosphatase activity and ultra-through analysis of the immune parameters of the large yellow croaker SOD activity of the two experimental groups are significantly increased(P<0.05), and lysozyme activity and superoxide dismutase of the group two were significantly higher than the group one(P<0.05). The results of challenge test showed that 7 days after infected the pathogenic Vibrio parahaemolyticus, the cumulative mortality of the group two and the group one were 10% and 50% lower than the control group respectively. Based on the results above, the conclusion can be drawn that non-specific immunity and the ability of resistance to pathogen infection of group two were significantly improved.Compound Chinese herbal polysaccharides(astragalus polysaccharides, angelica polysaccharide polysaccharide and coriolus versicolor polysaccharide) and matrine were respectively added to the basic feed of the large yellow croaker in a certain proportion of mixed. Aperiod of 49 days‘s feeding tests in seawater floating cages were carried out to investigate the diet containing matrine and compound Chinese herbal polysaccharides on the immunity and disease resistance of large yellow croaker. Results of the analysis of the immune parameters to the large yellow croaker show that compared to control group,serum bactericidal activity, lysozyme, acid phosphatase activity and ultra-SOD activity of two experimental groups were significantly increased(P<0.05) and serum bactericidal activity of matrine group was significantly higher than that of compound Chinese herbal polysaccharide group(P<0.05). The results of challenge test showed that 7 days after infected the pathogenic Vibrio parahaemolyticus, the cumulative mortality of the group one and the group two were 60% and 50% lower than the control group respectively. Based on the results above, the conclusion can be drawn that non-specific immunity and the ability of resistance to pathogen infection of two experimental groups were both significantly improved.